Self-adjusting pneumatic pressure switch



Feh 28 ww SELF-ADJUSTING PNEUMATIC PRESSURE SWITCH 5 Sheets-Sheet Filed July 24, 19 28 INVENTOR. 5 570007- VA B Feb. 23 31950 a. smum' SELF-ADJUSTING PNEUMATIC PRESSURE SWITCH Filed July 24, 1948 3 Sheets-Sheet 3 F'IIE 5.

FIEIEI IN V EN TOR.

Patented Feb. 28, 1950 SELF-ADJUSTING PNEUMATIC PRESSURE SWITCH Bernard Stoudt, Brooklyn, N. Y., assignor to Ames Spot Welder Co., Inc., Brooklyn, N. Y., a corporation of New York Application July 24, 1948, Serial No. 40,535

3 Claims.

This invention relates to air-operated pressure switches, and although it is presented herein as applied to air operated Welding machines the invention may be used for other purposes or in other applications.

The main object of the invention is the provision of a self-adjusting pneumatic pressure switch, including a cylinder having a plunger therein, which will prevent the closing of an electrical circuit until the gage pressure, that is, the pressure set and indicated on the pressure regulator, is reached. In the application of this invention to a spot welding machine, the invention assures the necessary pressure at the welder tips before current passes through the electrodes.

In the case of every cylinder having a piston therein, a certain amount of air pressure is required to overcome the inertia and friction of the piston and the parts driven by the piston. Therefore, regardless of the pressure exerted on the piston of a cylinder (which pressure in this example is regulated by a speed regulator), the percentage of air pressure required to perform the aforementioned function becomes less as the regulated gauge pressure becomes greater. Thus when the piston reaches the end of its stroke, the regulated gauge pressure is built up and the necessary pressure is exerted at the electrode points. At low gauge pressure, the pressure switch will close its contacts almost immediately after the electrode points meet. At high pressures, although the points close faster, there is a slightly longer lapse of time between the meeting of the points and the closing of the switch contacts. This condition is highly desirable in spot welding machines as it eliminates firing of the welder while the tips are bouncing (which is caused by the points at first hitting under higher air pressure). This assures uniform positive pressure on the Welding points at all times.

The above broad as well as additional and more specific objects will become apparent in the following description, wherein characters of reference refer to like-numbered parts in the accompanying drawings. It is to be understood that the drawings are intended for the purpose of illustration only, and that it is neither desired nor intended to limit the invention necessarily to any or all of the exact details of construction shown except insofar as they may be deemed essential to the invention.

Referring briefly to the drawings, Fig. 1 is a fragmentary side ele'vational view of a spot welding machine, showing fragmentarily the invention applied thereto, and including a wiring diagram.

Fig. 2 is a largely schematic view, partly in section, showing the air pressure cylinder, the pressure regulator, the operating valve, and in. central longitudinal cross-section, the pneumatic.

pressure switch of this invention, together with the piping connections of the various parts mentioned.

Fig. 3 is a sectional view taken on the line 33 of Fig. 2.

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 2.

Fig. 5 is a bottom plan view of the pneumatic pressure switch per se.

Fig. 6 is a sectional view taken on the line 66 of Fig. 2.

Fig. 7 is a sectional View taken on the line L-l of Fig. 8.

Fig. 8 is a sectional view taken on the line 88 of Fig. 2.

Referring in detail to the drawings, the numeral I0 indicates a cylindrical housing formed of two separable parts H and I2 and supported on and secured to a bracket I3 b means of, for example, socket bolts 1 4. The latter is provided with openings l5 through which screws or bolts, not shown, are adapted to be passed to mount the housing Ill on the frame or housing l6 of a spot welding machine. Screws ll join the cap l2 to the upper portion H of the housing ID.

The lower end of the housing In is closed by a disc or cover l8 provided with a raised axial boss 19 having a threaded opening 20 therethrough, an aligned opening 2| being provided in a plate 23a at the bottom of the housing H].

A cylindrical spacer 22 registers within the lower housing H and rests on the cap I8. A cylinder 23 registers between the boss l9 and the spacer 22 and is fixed in place. A plunger 24 is slidably mounted in the cylinder 23 and normally rests on a ring 25 registering in an appropriate peripheral groove in the boss IS. The plunger 24 is provided with a concentric bore 26 in an upward direction from the bottom, and a compression spring 27 has its lower end on the boss l9 and its upper end against the roof of the bore 26, normally urging the plunger upward. The plunger 24 has a socket 28 formed in the upper end thereof, the peripheral edge 29 of which is turned inward to form a lock flange by engaging a circumferential groove 38 in a head 3i of insulating material. A metal contact disc, which may be of silver and is shown at 32, is held on the head 3! by means of a screw 33. It is to be noted that the upper surface of the head is approximately conical or rounded and tapers toward the axis in an upward direction, and as a result the contact disc 32 possesses a degree of resiliency around its edge.

Secured by the screws I! as a partition between the housing II and the cap I2, is a cylindrical block 34 of insulating material which seals off the compartment 35 enclosed by the housing H from the compartment 36 enclosed by the cap l2. Spaced contact screws 3'! extend through the between and higher than the screws 3?.

A nipple 53- extends from the opening 28, and a nipple id extends from a similar threaded opening in the housing l i into the compartment 35. Air under pressure enters, through the pipe it, the pressure regulator ll and passes through a T 48. A pipe d9 connects one passage of the T 48 with the nipple M. A connection 50 leads the other passage of the T 68 into a control valve 5!, or, as it might be better termed, the operating Valve. This is a common type of valve, and from its two passages 52 and 53 pipes 55 and 5?, respec-. tively, extend. Air or exhaust vents are provided at 54 and 55. The valve cylinder 58, which is turned by the handle 59, has a wide radial passage to and a narrow radial passage Bl therethrough. Surface groove passages 62 and 63 are further provided in the cylinder 58. In the position of the valve shown in Fig. ,2, air entering through the passage into the cylinder 58 passes through the passage ti into the pipe 55, and air entering the valve from the pipe 51 passes through the passage 62 and out through the vent 55 into the atmosphere. When the handle 59 is moved to the left to the position shown in broken lines, air entering through the passage 63 will pass through the passage 6! into the pipe 57, and air entering the valve through the pipe 56 will pass through the passage 33 and through the vent 56 to th atmo p e ipe 58 e ds t n o the t o op n ng or a. standa d s ee uc r 64 o at 5, he other opening being shown at 66. Air flowin through the opening 6%! flows freely because owing to its pressure it lifts the ball 67 to enter the passage 68 and exit through the opening 65. However, air entering the opening can flow only through the passages 53 and H1, and owing to the restriction of the latter by the needle valve 1 H, the flow of air into the opening 66 is at reduced speed.

A pipe '12 leads from the opening 66 into the head end of a cylinder it. A pipe 14 leads from the nipple ts also to the head end of the said cylinder. A piston it; is slidable in the cylinder 73, and its rod 76 is pivoted, in the example illustrated, to a beam '58 at'i'i, the other end of the beam having a carriage '59 secured thereto and rigidly holding the upper electrode St. The pipe 51' is connected to the tail of the cylinder 13.

In the wiring diagram of Fig. l, the supply terminals are shown at 8!. The lead 35 is con.- nected to one terminal 8!. The other terminal 8! is connected to one terminal 82 of an electromagnet 83, and the lead all leads to the other terminal to of the latter. The switch contact 86 of the electromagnet leads to the lead 319 through a lead 87. The armature of the electrorna-gnet is connected to one terminal of the primary of a transformer 87, the other terminal of the said primary being connected by a lead 89 to the said other terminal at. The secondary of the transformer is connected by leads 9% and 9i with the upper and lower electrodes 80 and 92, respectively.

The air or pressure cylinder 13 is divided by the piston it into two chambers, the chamber 93 on the head side of the piston, and the chamber 9 3 on the tail side thereof.

The operating position of the o erating valve 5| is that shown in Fig. 2. The pressure which it is desired to apply to the welding points is attained in the regulator ll and indicated on the gauge thereof. Air flows from the regulator Lil through the pipe 49 into the chamber 35 of the housing ill. This static pressure holds down the plunger is and compresses the spring 21; thus, the contact disc 32 is held spaced from the two contact heads 38 of the binding posts 3'! and an open circuit is therefore maintained between the latter. Air from the regulator ll also flows through the T 48 and the operating valve 5i, thence through the pipe 55, through the speed regulator 64 and into the chamber 93 of the air cylinder '13, and finally this air also enters the hamber .26 Wi hin the pl nger 2 However. as the chamber 9.4 of the cylinder '53 is open to the a m h e h ugh t p 5 nd he ent 55 of the valve M, the piston it begins to move (downward, Fig. 2) before the regulated pressure is reached in the chamber 93, thus preventing the plunger 24 from rising to cause the disc 3 to touch the, contacts 38 to bridge the latter. As soon as the piston l5 has reached the limit of its travel (downward, Fig. 2), the air pressure in chambers 93 and 2t builds up to the regulated pressure shown on the gauge 95. However, just before the gauge pressure is attained in these chambers, the spring 27 starts to move the plunger 24 to cause the disc 32 to bridge the contacts 38. Thus at approximately the same instant the au e pressure is reached in the chamber 93 against the piston '55, thereby applying the desired pressure, as shown by the structure inFig. 1,

:, u o th upp r ldin electrode 80- Heno t e circuit through the electromagnet S3 and hence he cir u throv-shth e o es 39 an 2 are lo d a appro ima ely the in t nt when t e welding tips are joined against the, work, not

i shown.

When the position of the operating valve is reversed, air under pressure passes into the chamber 94 of the cylinder 13 to force the piston 15 toward its head end, and the air in the cha n.- ber 93 of the cylinder 13 and that in the chamber 26 of the plunger 24, is exhausted through the speed reducer (at a high rate of flow), the pip 56, and out of the valve 5! through the vent 54. Thus the plunger 24 is immediately forced down by the static pressure in the chamber 35, as this pressure remains unaltered, and the disc 32 breaks contact with the post contacts 38. The cycle of operations just described is then ready to be repeated.

In the appended claims the broader term fluid is used rather than the term air, as the device herein described and illustrated on the 801 companying drawin s may be operated by a liquid such as, for example, oil, or by any suitable gas other than air, as well as by air, all of which fall within the scope of the generic term fluid.

Obviously, modifications in form and struc. ture may be made without departing from the spirit or scope of the invention.

I claim:

1. In combination, a pressure actuated elec-. tric switch including a cylinder having a piston slidable therein, said cylinder having a passage through the wall thereof into the head portion of the interior of the cylinder, said cylinder having a passage through the tail end thereof, spaced electric contacts projecting from said cylinder head into said head portion of the interior of the cylinder, said piston having a metallic member 75 thereon of greater length than the distance be:

5 tween said contacts, said member being adapted to bridge said contacts when said piston is positioned at the head end of its stroke, resilient means normally urging said piston toward said head end, a fluid conduit connected at one end with said first-named passage, a fluid conduit connected at one end with said second-named passage, a second cylinder having a piston slidable therein, said second cylinder having a passage through the head end thereof and a passag through the tail end thereof, the other end of said second-named conduit being connected with said first-named passage of said second cylinder, a main conduit adapted to have fluid under pressure fed thereinto, a third fluid conduit also connected at one end with said firstnamed passage of said second cylinder, the other ends of said first-named conduit and said third conduit being connected with said main conduit, and a pressure regulating valve in said main conduit adapted to pass fluid under a given pressure through said first-named and third-named conduits, said second-named piston upon admittance of said fluid through said valve being moved thereby toward its tail end thereby preventing buildin up of pressure in the tail end of said first-named cylinder until said secondnamed piston has reached the end of its stroke whereupon the fluid in said tail end of said firstnamed cylinder builds up to the value of said given pressure so that the latter added to the force of said spring moves said first-named piston to the head end of said first-named cylinder thereby engaging said metallic member with said contacts.

2. A fluid pressure apparatus comprising a main conduit adapted to have fluid fed thereinto, a pair of branch fluid conduits connected with said main conduit, a cylinder having a passage through the head end thereof and a passage through the tail end thereof, a piston in said cylinder, one of said branch conduits being connected with said head end passage of said cylinder, a third fluid conduit connected at one end with said head end passage of said cylinder, a housing having a piston slidable therein, said housing having a passage therethrough into the head end thereof and also having a passage therethrough into the tail end thereof, a spring normally urging said second-named piston toward the head end of its said cylinder, the

other of said branch conduits being connected with said head end passage of said housing, the other end of said third fluid passage being connected with said tail end passage of said housing, and a pressure regulating valve in said main conduit whereby upon opening said valve fluid under given pressure passes through said branch conduits, said fluid in said other branch conduit passing into said head end of said housing and filling said head end of said housing with fluid at said given pressure thereby urging said secend-named piston against and compressing said spring, said fluid entering said tail end passage of said housing having at first a lower pressure than said given pressure owing to the retarda" tion of building up pressure in said third conduit caused by said fluid in said one of said branch conduits causing said first-named piston to travel toward the tail end of its stroke, the pressure of said fluid in said cylinder and hence in said one of said branch conduits and in said tail end of said housing then after said firstnamed piston reaches its said tail end of its stroke building up to equal said given pressure so that the latter added to the force of said spring moves said second-named piston toward the head end of said housing.

3. The apparatus set forth in claim 2, having a circuit closer comprising at least two electric contacts, one of said contacts being mounted on said housing within the housing, the other of said contacts being mounted on said secondnamed piston and adapted to contact said one of said contacts when said piston has moved toward the end of said housing as aforesaid to approximately the end of its said stroke.

BERNARD STOUDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,542,931 Foote June 23, 1925 2,085,105 Lex June 29, 1937 2,126,490 Martin Aug, 9, 1938 2,293,393 Humphrey Aug. 18, 1942 2,431,674 Baak Dec. 2, 1947 

